Most personal computers today utilize direct access storage devices (DASD) or rigid disk drives for data storage and retrieval. Present disk drives include a disk rotated at high speeds and a read/write head that, in industry parlance, xe2x80x9cfliesxe2x80x9d a microscopic distance above the disk surface. The disk includes a magnetic coating that is selectively magnetizable. As the head flies over the disk, it xe2x80x9cwritesxe2x80x9d information, that is, data, to the hard disk drive by selectively magnetizing small areas of the disk; in turn, the head xe2x80x9creadsxe2x80x9d the data written to the disk by sensing the previously written selective magnetizations. The read/write head is affixed to the drive by a suspension assembly and electrically connected to the drive electronics by an electrical interconnect. This structure (suspension, electrical interconnect, and read/write head) is commonly referred to in the industry as a Head Gimbal Assembly, or HGA.
More specifically, currently manufactured and sold read/write heads include an inductive write head and a magnetoresistive (MR) read head or element or a xe2x80x9cgiantxe2x80x9d magnetoresistive (GMR) element to read data that is stored on the magnetic media of the disk. The write head writes data to the disk by converting an electric signal into a magnetic field and then applying the magnetic field to the disk to magnetize it. The MR read head reads the data on the disk as it flies above it by sensing the changes in the magnetization of the disk as changes in the voltage or current of a current passing through the MR head. This fluctuating voltage in turn is converted into data. The read/write head, along with a slider, is disposed at the distal end of an electrical interconnect/suspension assembly.
An exploded view of a typical electrical interconnect/suspension assembly is shown in FIG. 1, which illustrates several components including a suspension A and an interconnect B. It will be understood that the actual physical structures of these components may vary in configuration depending upon the particular disk drive manufacturer and that the assembly shown in FIG. 1 is meant to be illustrative of the prior art only. Typically, the suspension A will include a base plate C, a radius (spring region) D, a load beam E, and a flexure F. At least one tooling discontinuity 70 G may be included. An interconnect B may include a base H, which may be a synthetic material such as a polyimide, that supports typically a plurality of electrical traces or leads I of the interconnect. The electrical interconnect B may also include a polymeric cover layer that encapsulates selected areas of the electrical traces or leads I.
Stated otherwise, suspension A is essentially a stainless steel support structure that is secured to an armature in the disk drive. The read/write head is attached to the tip of the suspension A with adhesive or some other means. The aforementioned electrical interconnect is terminated to bond pads on the read/write head and forms an electrical path between the drive electronics and the read and write elements in the read/write head. The electrical interconnect is typically comprised of individual electrical conductors supported by an insulating layer of polyimide and typically covered by a cover layer.
As mentioned previously, the slider xe2x80x9cfliesxe2x80x9d only a microscopic distancexe2x80x94the xe2x80x9cfly heightxe2x80x9dxe2x80x94above the spinning media disk. Control of fly height is critical for the operation of a disk drive. If the fly height is too large, the read/write head will not be able to read or write data, and if it is to small, the slider can hit the media surface, or crash, resulting the permanent loss of stored data. As such, the fly height of the slider is determined in much part by the characteristics of the head suspension assembly to which it is mounted. The head suspension imparts a vertical load, commonly referred to as xe2x80x9cgram loadxe2x80x9d, on the slider, normal to the surface of the disk, in order to oppose the xe2x80x9cliftxe2x80x9d forces created by the air passing between the slider and the spinning disk. As a result, head suspension assemblies are manufactured with a very precise gram load, typically with a tolerance of xc2x10.2 grams. Another head suspension assembly characteristic that has a significant effect upon the fly height of a slider, is referred to as xe2x80x9cstatic attitudexe2x80x9d. Static attitude is the angular attitude of the gimbal to which the slider is mounted. Typically, head suspension assemblies are manufactured with tolerances for static attitude approaching xc2x130 arc-minutes.
Successful reading or writing of data between the head and the spinning media also requires that the head be precisely positioned directly above the location on the disk to which data is to be written or read. As such, great care is taken to design and manufacture head suspension assemblies so as to optimize the suspension""s vibrational, or resonant, performance.
There are three basic configurations of electrical interconnect/suspension assemblies that are currently utilized in the disk drive industry. With the first, a Trace Suspension Assembly, or TSA, the electrical interconnect is fabricated integrally with the flexure. The TSA flexure/interconnect is fabricated by selectively removing material from a laminate of stainless steel, polyimide, and copper. The TSA flexure/interconnect is then attached to a loadbeam, typically with one or more spot welds between the stainless steel layer of the TSA flexure/interconnect and the stainless steel of the loadbeam.
Another interconnect configuration, termed CIS, is very similar to TSA in that the CIS interconnect is also fabricated integrally with the flexure. However, the CIS interconnect/flexure is fabricated with xe2x80x9cadditivexe2x80x9d processes, rather than xe2x80x9csubtractivexe2x80x9d processes. The CIS interconnect/flexure is attached to a load beam in much the same manner as the TSA flexures and conventional flexures are, with one or more spot welds between the stainless steel of the flexure and that of the loadbeam.
The last interconnect configuration that is utilized today by disk drive assemblers is essentially a flexible circuit. The flexible circuit consists of a base polymer, typically a polyimide, which supports copper traces, or leads. In this case, the interconnect is fabricated independently from the flexure, and is later adhesively attached to a conventional head suspension assembly, to form a Flex Suspension Assembly, or FSA.
The attachment of conventional flexures to load beams with spot welds has been practiced for years throughout the head suspension industry and is well understood. Thus, the attachment of a CIS or TSA interconnect/flexure to a loadbeam utilizes existing techniques, and does not present any significant challenges for manufacturers of head suspension assemblies. On the other hand, adhesive attachment of flexible circuits to conventional head suspension assemblies results in a number of issues which the manufacturer of head suspension assemblies must address. For example, the conventional suspension to which the electrical interconnect is attached, is manufactured with great care to ensure that the gimbal is at the prescribed static attitude. But when the electrical interconnect is bonded to the conventional suspension assembly, the static attitude of the gimbal is altered relative to the angular attitude of the gimbal region of the electrical interconnect, thereby increasing the static attitude variation and changing the static attitude average of the completed head suspension assembly/electrical interconnect.
While FSA is significantly cheaper than it""s counterparts, namely TSA and CIS, the degradation in FSA performance due to the adhesive attachment of the flexible circuit creates a tradeoff between cost and performance that must be considered when comparing the competing technologies.
As such, it is the object of the present invention to eliminate the degradation in FSA performance associated with the adhesive attachment of the flexible circuit to the head suspension assembly. More specifically, it is the object of the present invention to minimize the change in static attitude of the gimbal of a head suspension assembly during the adhesive attachment of a flexible circuit to a head suspension assembly.
It is an object of the present invention to provide a method of producing an electrical interconnect which is attached to a conventional head suspension assembly without significantly affecting the static attitude attributes of the head suspension assembly.
It is an object of the present invention to provide an electrical interconnect which is attached to a conventional head suspension assembly without significantly affecting the static attitude attributes of the head suspension assembly.
The present invention is directed to a head suspension assembly/electrical interconnect that cantilevers a read/write magnetic transducer head adjacent the rotating surface of a disk in a disk drive from an actuator arm of the disk drive, and the method of constructing the head suspension/electrical interconnect assembly. The present invention includes both methods and designs intended to minimize the change of the head suspension gimbal""s static attitude resulting from the adhesive attachment of an electrical interconnect, thereby improving the manufacturing yields and performance of the head suspension assembly/electrical interconnect.
The present invention accomplishes the foregoing aims and goals by providing a web out of which the electrical interconnect is formed, the web having at least a bottom layer of a synthetic material supporting a conductive material. The conductive layer is selectively removed to form the electrical leads or traces, thus forming an interconnect blank. Subsequent to the formation of the traces, the bottom support layer is selectively removed, thus forming an interconnect blank that is still attached to the web by a pair of tension tabs composed of the bottom (or substrate) material. These tabs provide a tension directed in a direction angularly disposed to the longitudinal axis of the interconnect blank. The interconnect blank is then severed from the web, with the tension tabs exerting a laterally directed tension, thereby substantially inhibiting deformation of the gimbal region of the interconnect and the creation of non-planar slider standoffs.
The foregoing objects of the invention will become apparent to those skilled in the art when the following detailed description of the invention is read in conjunction with the accompanying drawings and claims. Throughout the drawings, like numerals refer to similar or identical parts.